Thanks – exactly where should that be insterted, and which functions.php file? We put it at the bottom of the one in wp-includes, and it crashed the site.
We solved it by updating the routing, thanks, now it saves the api key but doesn’t connect – it says API call to helper/ping failed: SSL certificate problem: unable to get local issuer certificate.
Sun Oct 25 21:54:06.649175 2015] [:error] [pid 3524:tid 1100] [client ::1:60854] PHP Fatal error: Call to undefined function curl_init() in C:\\Apache24\\htdocs\\grubdujour\\wp-content\\plugins\\yikes-inc-easy-mailchimp-extender\\includes\\MailChimp\\Mailchimp.php on line 144, referer: https://localhost:8080/grubdujour/wp-admin/admin.php?page=yikes-inc-easy-mailchimp-settings